Imagine millions of tiny prisms in the sky refracting moonlight on a cool night, just for you. That’s exactly what happens when you look up and see a ring or “halo” around the moon. The prisms in this case are millions of tiny hexagonal-shaped ice crystals in cirrus clouds 20,000 feet in the sky. The six-sided crystals are splitting the light and bending it toward your eyes- your eyes in particular because no one sees exactly the same lunar halo created by the same ice crystals. Each lunar halo is unique to each observer. In folklore a halo around the moon meant that rain was on the way- "Ring around the moon, rain is coming soon," which may be true because high cirrus clouds often lead a storm front. Enjoy a time-lapse video below I made of a lunar halo on June 27th in Hamilton, Ala.